CussEN. — On tJic Piako and Waikato Bivcr-haains. 405 



upper portions of the plain, by Matamata. The aUuvial beds 

 of the lower areas of the Piako basin from the confluence of 

 the "Waitoa and Piako to the sea differ in a very remarkable 

 manner from those higher up, and in the Waikato basins. 

 Here we find a heavy argillaceous deposit similar to that of 

 the Waipa Eiver. A large area on the western side, and be- 

 tween the Piako and Thames Eivers, is covered with it. The 

 land is extremely fertile, and if it could be drained would be 

 some of the best soil in the country. The source from wliich 

 the alluvium came is an interesting question. That it should be 

 found in the lower area of the valley, whilst higher up, on the 

 plains of Piako, Te Aroha, and Matamata, the alluvial deposits 

 are of pumice and sands similar to those in the Waikato 

 basins, is not easy to explain. The tributaries of the Piako 

 may have brought down clay-alluvium from the Maungakawa 

 Eanges, but it would necessarily be limited in quantity, from 

 the small area of the ranges which they drain. I think it best 

 explained by supposing it to have been brought down by the 

 Waipa Eiver from the limestone land in the King-country 

 previously to the great upheaving and changes in the Waikato 

 basins, and laid down in the lower part of the Piako 

 Valley as an estuarine deposit when the Hauraki Gulf ex- 

 tended further inland. There is some evidence to favour this 

 supposition. The Mangawhara Stream rises near Hoeatainui, 

 within three miles of the Piako Eiver at its confluence with 

 the Waitoa. A low saddle in the fern-ridge w^liich separates 

 the head waters of the Mangaw'hara from the Piako Valley 

 would seem to have been eroded by a river. Terraces are 

 traceable on either side of the saddle. At Hoeatainui, and all 

 along the Mangawhara Valley to the junction of the river with 

 the Waikato at Taupiri, the alluvium is of similar character to 

 that of the Lower Piako Valley. It seems probable, there- 

 fore, that at one time the Waipa occupied the Mangawhara 

 Valley, and flowed into the Hauraki Gulf at Maukoro. 



From the foregoing observations it would appear that the 

 Waikato Eiver for a long period of its history has undergone 

 successive changes in its course. At each change it would 

 appear to have left its natural valley, and, turning to the west- 

 ward, found a new course through the ranges which separate 

 one valley from the others. Each basin would appear to have 

 had extensive lakes situated within it. The present topo- 

 graphical features of the country do not afford sufficient 

 evidence of the causes which effected these changes. If the 

 levels of the country were as we find them to-day there would 

 be nothing to impede the Waikato Eiver in its old and natural 

 course by the Hinuwera Valley to the Hauraki Gulf. And 

 the contour of the Middle Waikato basin would not permit of 

 the existence of the lake : neither would the Waikato Eiver 



